Obscuring and feeding supermassive black holes with evolving nuclear star clusters

TL;DR

This paper combines high-resolution observations and hydrodynamical simulations to study the evolution of nuclear star clusters and their role in feeding supermassive black holes, linking large-scale gas inflows to parsec-scale accretion discs.

Contribution

It introduces a two-stage modeling approach connecting large-scale gas dynamics with parsec-scale nuclear discs in active galaxies.

Findings

Predicted nuclear disc sizes of 0.8-0.9 pc.

Gas masses around 10^6 solar masses.

Mass transfer rates of 0.025 solar masses per year.

Abstract

Recently, high resolution observations with the help of the near-infrared adaptive optics integral field spectrograph SINFONI at the VLT proved the existence of massive and young nuclear star clusters in the centres of a sample of Seyfert galaxies. With the help of high resolution hydrodynamical simulations with the PLUTO-code, we follow the evolution of such clusters, especially focusing on mass and energy feedback from young stars. This leads to a filamentary inflow of gas on large scales (tens of parsec), whereas a turbulent and very dense disc builds up on the parsec scale. Here, we concentrate on the long-term evolution of the nuclear disc in NGC 1068 with the help of an effective viscous disc model, using the mass input from the large scale simulations and accounting for star formation in the disc. This two-stage modelling enables us to connect the tens of parsec scale region (observable with SINFONI) with the parsec scale environment (MIDI observations). At the current age of the nuclear star cluster, our simulations predict disc sizes of the order of 0.8 to 0.9 pc, gas masses of 1.0e6 Msun and mass transfer rates through the inner boundary of 0.025 Msun/yr in good agreement with values derived from observations.